Plugged Duemilanove back into Vista PC today - same upload error as described in forums. Messed with boards.txt and serial settings - no luck.

Switched to XP box, same problem.

Unit finally started working when I ran a multimeter between Gnd and pin 1 (reset) on the ATIMEGA328 chip (to check pin voltage) and pressed the Reset button. Suddenly the old program on the board reloaded and I could upload fine.

Hey did anybody face this problem on windows 7!!??im facing it..and its difficult to get out of this..my arduino is a brand new duemilanove .opened it today..and uploaded the blink program..and whoaa!! error!!!and the twist here is..i got the led blink when i disconnected and connected the usb back..but with the same error written ..when i edited the delay periods..nothing changed much..however i could see some erratic behaviour of the led for sometime..and then it conitued to blink in the similar earlier fashion..i particularly doubt the drivers which were automatically installed at the startup..but arduino.cc says ..it works!! on vista..and so it should on 7 too...!!but why is the problem persisting.!!guys..help me out!!

I had this problem, and I was just now able to solve it by using a modified method from this thread. I am using a sparkfun FT232R breakout board, and a breadboard arduino tutorial from here. I use the usb breakout board to provide +5v, gnd, TX, and RX. To get the sketch to upload, I plug in the usb cable, hold down the reset button on the arduino, and then release the reset button when the "code compiled" message comes up.

I'm using an intel Mac and had the rapid flashing pin 13 problem. It started I think because I'm dual boot with windows and rebooted into window while the arduino was plugged in but I don't ever use it on the windows side. When I switched back to Mac later I noticed the Rapid flashing and I couldn't upload a new sketch.

I finally fixed it using the method of holding the reset while I plugged it in, uploading a sketch and letting go of reset right after compiling ended and upload was just starting.

I had this very same problem with my brand new arduino nano v3.0It turned out that my nano had a 168 chip, not 328, wich i was certain it had. When this was corrected in the IDE, everything works great.